This invention relates to a self-levelling boom arrangement for supporting upon a frame of an agricultural material distribution device.
Agricultural material distribution devices have been proposed for many years including sprayers and various types of pneumatic spreaders for granular or powdered material. Larger devices of this type tend to have a boom which is supported by wheels at the ends or along the length together with a central support at a material transport truck arrangement. In these cases the height of the boom relative to the ground is controlled to a great extent by the wheels so that provided there is flexibility between the portions of the boom, it tends to maintain a proper height relative to the ground.
Other devices of this type have a centrally supported boom with boom arms which extend outwardly to respective sides of a central frame portion with a plurality of nozzles or jets arranged along the length of the arms for spreading the material in controlled fans along the length of the boom. It will be appreciated that if the boom changes its height relative to the ground, then the fan developed by one nozzle or jet will either overlap with or be spaced from the fan of the next adjacent nozzle, thus altering the amount of material applied to the ground and detracting from the proper distribution of the material.
Changes of height of the boom relative to the ground can occur in two different ways. Firstly, the frame supporting the central truck device and support for the boom can tilt should the frame move over uneven ground whereupon one arm of the boom will move closer to the ground and the other will be lifted away from the ground. In other cases the frame can remain level while the ground on one side of the frame raises or lowers at a ditch or the like.
In view of the above problems concerning proper distribution, it is extremely desirable to be able to control and self-level the boom so that as far as possible the height of the boom remains constant relative to the ground.
It is one object of the present invention, therefore, to provide an improved boom arrangement of this type which is effectively self-levelling.
According to the invention, therefore, there is provided a self-levelling boom arrangement for supporting upon a frame of an agricultural material distribution device comprising a pair of boom arms each arranged to extend outwardly to one side of the frame and including means for spreading said material along the length of the arms, a central support member, pivotal mounting means for mounting each of said arms on said central support member for pivotal movement relative thereto about a substantially horizontal axis at right angles to the length of the arm, two linkage means each pivotally connected to a respective one of said arms at a position spaced from said pivotal mounting means and arranged for pivotal attachment to said frame and means for mounting said central support member on said frame for side to side movement of said pivotal mounting means relative to said frame whereby said boom arms are moved relative to said frame on tilting of said frame relative to the vertical to tend to self-level said arms.
According to a second aspect of the invention, therefore, there is provided a self-levelling boom arrangement for supportng upon a frame of an agricultural material distribution device comprising a pair of boom arms each arranged to extend outwardly to one side of the frame and including means for spreading said material along the length of the arms, a central support member, pivotal mounting means for mounting each of said arms on said central support member for pivotal movement relative thereto about a substantially horizontal axis at right angles to the length of the arm, two linkage means each pivotally connected to a respective one of said arms at a position spaced from said pivotal mounting means and arranged for pivotal attachment to said frame, said linkage means including means for raising and lowering the respective arm independently of the other arm and means for mounting said central support member on said frame for side to side movement of said pivotal mounting means relative to said frame whereby said boom arms can be independently raised and lowered while providing a self-levelling effect to tend to accommodate tilting of the frame relative to the vertical.
It is one advantage of the invention, therefore, that the arms can be raised and lowered independently of one another while retaining the self-levelling effect which tends to accommodate tilting of the same relative to the vertical.
This can be provided by an arrangement in which the central support member comprises a simple vertical beam pivoted at a lower end with the arms pivotally connected to the beam at a single point, thus providing a symmetrical arrangement which is effectively self-levelling by the side to side movement of the beam provided by the pivotal coupling at the bottom of the beam.
The linkages can be in the form of hydraulic rams coupled to the arms outwardly of the central beam and extending upwardly and inwardly therefrom for connection to the frame so that actuation of one of the rams raises or lowers the respective arm independently while the central support beam remains central to accommodate tilting of the frame.